Bottom Line:
Our results showed Tibetan wild barley distinctly diverged from Near Eastern barley, and confirmed that Tibet is one of the origin and domestication centers for cultivated barley, and in turn supported a polyphyletic origin of domesticated barley.Two unique haplotypes (Hap2 and Hap7) caused by a base mutations (at position 544) in the coding region of the NAM-1 gene might have a significant impact on the GPC.Single nucleotide polymorphisms and haplotypes of NAM-1 associated with GPC in barley could provide a useful method for screening GPC in barley germplasm.

Affiliation: College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China.

ABSTRACTThe origin, evolution, and distribution of cultivated barley provides powerful insights into the historic origin and early spread of agrarian culture. Here, population-based genetic diversity and phylogenetic analyses were performed to determine the evolution and origin of barley and how domestication and subsequent introgression have affected the genetic diversity and changes in cultivated barley on a worldwide scale. A set of worldwide cultivated and wild barleys from Asia and Tibet of China were analyzed using the sequences for NAM-1 gene and gene-associated traits-grain protein content (GPC). Our results showed Tibetan wild barley distinctly diverged from Near Eastern barley, and confirmed that Tibet is one of the origin and domestication centers for cultivated barley, and in turn supported a polyphyletic origin of domesticated barley. Comparison of haplotype composition among geographic regions revealed gene flow between Eastern and Western barley populations, suggesting that the Silk Road might have played a crucial role in the spread of genes. The GPC in the 118 cultivated and 93 wild barley accessions ranged from 6.73 to 12.35% with a mean of 9.43%. Overall, wild barley had higher averaged GPC (10.44%) than cultivated barley. Two unique haplotypes (Hap2 and Hap7) caused by a base mutations (at position 544) in the coding region of the NAM-1 gene might have a significant impact on the GPC. Single nucleotide polymorphisms and haplotypes of NAM-1 associated with GPC in barley could provide a useful method for screening GPC in barley germplasm. The Tibetan wild accessions with lower GPC could be useful for malt barley breeding.

Figure 1: Geographic distribution of wild barley populations and landrace populations.NAM-1 haplotype frequencies among nine geographic regions were displayed in pie diagrams and the exact proportions of each are given in percent by the corresponding color code.

Mentions:
The haplotype frequencies present in all accessions ranged from 0.005 to 0.449. Among all the haplotypes, three haplotypes were detected in 193 barley accessions. The haplotype Hap2 appeared in 96 accessions (44.9%), Hap7 was observed in 80 accessions (37.4%), and Hap1 was present in 17 accessions (7.9%). Of the seven haplotypes present in <2% of the accessions sampled, five were unique to the specific wild populations, i.e., Hap3 and Hap8 was unique to the Southwest Asian wild barley population and the Tibetan wild barley populations, respectively. The frequencies of NAM-1 haplotypes differed markedly among different geographic populations. The haplotype Hap1 was the most frequent one in the Southwest Asian wild barley population (0.264), but rare in the North American and European landraces (0.063 and 0.10, respectively), and absent in the remaining six populations. The rare haplotypes either confined or occurred in specific geographic regions, i.e., the Hap2 was detected in a few landrace accessions from North America (0.063), and the Hap3 (0.075), Hap5 (0.057), and Hap6 (0.057) were population-specific to wild barley in Southwest Asia; Hap8 and Hap10 were unique to the wild population in Tibet (Table 2; Figure 1).

Figure 1: Geographic distribution of wild barley populations and landrace populations.NAM-1 haplotype frequencies among nine geographic regions were displayed in pie diagrams and the exact proportions of each are given in percent by the corresponding color code.

Mentions:
The haplotype frequencies present in all accessions ranged from 0.005 to 0.449. Among all the haplotypes, three haplotypes were detected in 193 barley accessions. The haplotype Hap2 appeared in 96 accessions (44.9%), Hap7 was observed in 80 accessions (37.4%), and Hap1 was present in 17 accessions (7.9%). Of the seven haplotypes present in <2% of the accessions sampled, five were unique to the specific wild populations, i.e., Hap3 and Hap8 was unique to the Southwest Asian wild barley population and the Tibetan wild barley populations, respectively. The frequencies of NAM-1 haplotypes differed markedly among different geographic populations. The haplotype Hap1 was the most frequent one in the Southwest Asian wild barley population (0.264), but rare in the North American and European landraces (0.063 and 0.10, respectively), and absent in the remaining six populations. The rare haplotypes either confined or occurred in specific geographic regions, i.e., the Hap2 was detected in a few landrace accessions from North America (0.063), and the Hap3 (0.075), Hap5 (0.057), and Hap6 (0.057) were population-specific to wild barley in Southwest Asia; Hap8 and Hap10 were unique to the wild population in Tibet (Table 2; Figure 1).

Bottom Line:
Our results showed Tibetan wild barley distinctly diverged from Near Eastern barley, and confirmed that Tibet is one of the origin and domestication centers for cultivated barley, and in turn supported a polyphyletic origin of domesticated barley.Two unique haplotypes (Hap2 and Hap7) caused by a base mutations (at position 544) in the coding region of the NAM-1 gene might have a significant impact on the GPC.Single nucleotide polymorphisms and haplotypes of NAM-1 associated with GPC in barley could provide a useful method for screening GPC in barley germplasm.

Affiliation:
College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China.

ABSTRACTThe origin, evolution, and distribution of cultivated barley provides powerful insights into the historic origin and early spread of agrarian culture. Here, population-based genetic diversity and phylogenetic analyses were performed to determine the evolution and origin of barley and how domestication and subsequent introgression have affected the genetic diversity and changes in cultivated barley on a worldwide scale. A set of worldwide cultivated and wild barleys from Asia and Tibet of China were analyzed using the sequences for NAM-1 gene and gene-associated traits-grain protein content (GPC). Our results showed Tibetan wild barley distinctly diverged from Near Eastern barley, and confirmed that Tibet is one of the origin and domestication centers for cultivated barley, and in turn supported a polyphyletic origin of domesticated barley. Comparison of haplotype composition among geographic regions revealed gene flow between Eastern and Western barley populations, suggesting that the Silk Road might have played a crucial role in the spread of genes. The GPC in the 118 cultivated and 93 wild barley accessions ranged from 6.73 to 12.35% with a mean of 9.43%. Overall, wild barley had higher averaged GPC (10.44%) than cultivated barley. Two unique haplotypes (Hap2 and Hap7) caused by a base mutations (at position 544) in the coding region of the NAM-1 gene might have a significant impact on the GPC. Single nucleotide polymorphisms and haplotypes of NAM-1 associated with GPC in barley could provide a useful method for screening GPC in barley germplasm. The Tibetan wild accessions with lower GPC could be useful for malt barley breeding.